1. Field of the Invention
The present invention relates to an optical gain equalizer for eliminating level deviation of a wavelength division multiplexing light due to wavelength dependency of gain of an erbium doped optical fiber amplifier and wavelength dependency of a transmission system, and an optical amplifier and a wavelength-division multiplex transmitter both comprising such an optical gain equalizer.
2. Related Background Art
Long distance and great capacity optical transmission techniques which have remarkably been progressed in recent years are technically based on an optical fiber amplifier using a rare earth doped optical fiber and a wavelength division multiplexing (referred to as xe2x80x9cWDMxe2x80x9d hereinafter) transmission.
Nowadays, many optical fiber amplifiers using an orbium doped optical fiber have been developed and put to practical use in various fields, as well as the transmission systems. On the other hand, gain of the optical fiber amplifier has wavelength dependency. Accordingly, when the optical fiber amplifier is used in the WDM transmission system, and particularly when a number of optical fiber amplifiers are interconnected in a cascade manner, the wavelength dependency of the gain arises a problem. If the gain has the wavelength dependency, level deviation is generated in an amplified wavelength division multiplexing light, thereby deteriorating cross-talk between wavelengths and worsening setting of light receiving level of a receiver.
Although the optical fiber amplifier itself has been developed to minimize its gain wavelength dependency, in the WDM transmission system in which the amplifiers are interconnected in a multi stage manner, in order to eliminate the wavelength dependency of the gain of each optical fiber amplifier, optical gain equalizers are used.
Regarding the optical gain equalizer, although an equalizer using an etalon filter, an equalizer using an optical fiber coupler, an equalizer using an interference film filter comprised of a dielectric multilayer film, an equalizer using grating (fiber-type grating or grating provided on a glass substrate), an equalizer using a Mach-Zehnder type optical filter and the like have been developed, for several reasons (Japanese Patent Application No. 9-289349 (1997) describes kinds and problems of the optical gain equalizer), the equalizer using the etalon filter has been expected.
The etalon filter has a sinusoidal wave loss characteristic, so that loss characteristic having desired wavelength dependency can be created by combining a plurality of etalon filters having different characteristics. Thus, in the optical gain equalizer, as shown in FIG. 9, a plurality of etalon filters A having a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of a gain curve for gain flattening are prepared, and these filters are arranged in cascade, so that a light (wavelength division multiplexing light) between optical fibers D and E is passed through the group of filters by using collimator lenses B, C, thereby completely eliminating the wavelength dependency of the gain.
In the optical gain equalizer obtained by combining the etalon filters A shown in FIG. 9, in principle, the greater the number of filters to be combined, the more complete elimination of the wavelength dependency of the gain. However, in consideration of manufacturing viewpoint and total permeation loss, the number of etalon filters which can be combined is limited to about four. Accordingly, it is difficult to eliminate the wavelength dependency of the gain completely, and substantial flattening becomes about 1 dB.
An object of the present invention is to provide an optical gain equalizer in which gain wavelength dependency of an optical fiber amplifier can be compensated to an error of about 0.1 dB by utilizing etalon filters and in which deviation dependency of permeability is small and which can easily be manufactured. Another object of the present invention is to provide an optical fiber amplifier in which wavelength dependency of gain becomes small by using such an optical gain equalizer and a wavelength-division multiplex transmitter in which such optical fiber amplifiers in a multi-stage manner.
In an optical gain equalizer according to a first aspect of the present invention, a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges.
In an optical gain equalizer according to a second aspect of the present invention, a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening.
In an optical gain equalizer according to a third aspect of the present invention, a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters.
In an optical gain equalizer according to a fourth aspect of the present invention, a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters.
According to a fifth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and a first optical amplifier for amplifying a wavelength division multiplexing light.
According to a sixth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and a first optical amplifier for amplifying a wavelength division multiplexing light.
According to a seventh aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light.
According to an eighth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light.
According to a ninth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier.
According to a tenth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon fibers have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier.
According to an eleventh aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier.
According to a twelfth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier.
According to a thirteenth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and first and second optical amplifiers for amplifying a wavelength division multiplexing light.
According to a fourteenth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and first and second optical amplifiers for amplifying a wavelength division multiplexing light.
According to a fifteenth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light.
According to a sixteenth aspect of the present invention, an optical amplifying device comprises an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light.
According to a seventeenth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers.
According to an eighteenth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers.
According to a nineteenth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers.
According to a twentieth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers.
According to a twenty-first aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a twenty-second aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a twenty-third aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a twenty-fourth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a twenty-fifth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical fiber amplifier.
According to a twenty-sixth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical fiber amplifier.
According to a twenty-seventh aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical fiber amplifier.
According to a twenty-eighth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical fiber amplifier.
According to a twenty-ninth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a thirtieth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a thirty-first aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a thirty-second aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical fiber amplifier.
According to a thirty-third aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical fiber amplifier.
According to a thirty-fourth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical fiber amplifier.
According to a thirty-fifth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical fiber amplifier.
According to a thirty-sixth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical fiber amplifier.
According to a thirty-seventh aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a thirty-eighth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a thirty-ninth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a fortieth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a forty-first aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical semiconductor amplifier.
According to a forty-second aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical semiconductor amplifier.
According to a forty-third aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical semiconductor amplifier.
According to a forty-fourth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and a first optical amplifier for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged before or after the first optical amplifier and the first optical amplifier is an optical semiconductor amplifier.
According to a forty-fifth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a forty-sixth aspect of the present invention, three is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a forty-seventh aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a forty-eighth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the first optical amplifier is an optical semiconductor amplifier.
According to a forty-ninth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical semiconductor amplifier.
According to a fiftieth aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical semiconductor amplifier.
According to a fifty-first aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical semiconductor amplifier.
According to a fifty-second aspect of the present invention, there is provided an optical amplifying device comprising an optical gain equalizer in which a plurality of etalon filters and one or more fiber gratings or dielectric multilayer filters are arranged in cascade, and a beam of light externally applied is passed through the etalon filters and the one or more fiber gratings or dielectric multilayer filters and outputted to the outside, and the etalon filters have different free spectrum ranges, and have a sinusoidal wave loss characteristic of the same amplitude and period as those of the term obtained by Fourier series expansion of the loss wavelength characteristic for gain flattening, and the one or more fiber gratings or dielectric multilayer filters compensate the ripple component remaining as the difference between the loss wavelength characteristic for gain flattening and the loss wavelength characteristic owing to the etalon filters; and first and second optical amplifiers for amplifying a wavelength division multiplexing light, and wherein the optical gain equalizer is arranged between the first and second optical amplifiers and the first optical amplifier is an optical semiconductor amplifier.
According to a fifty-third aspect of the present invention, there is provided a wavelength division multiplex transmitter comprising a light sending device 10 including a light sending portion 7 for sending a plurality of signal lights having different wavelengths, and a light combining device 9 for outputting a wavelength division multiplexing light obtained by combining the plurality of signal lights to one end of an optical transmitting path 8; a light receiving device 13 including a light dividing device 11 for dividing the wavelength division multiplexing light outputted from the other end of the optical transmitting path 8 into signal lights for each wavelength, and a light receiving portion 12 for converting the divided signal lights into respective electrical signals; and one or more optical amplifying devices 14 disposed between the light sending device 10 and the light receiving device 13 and adapted to amplify the wavelength division multiplexing light propagated through the optical transmitting path 8, and wherein the optical amplifying device 14 is an optical amplifying device according to any one of fifth to fifty-second aspects.